The ones I own and use don’t really have any shorter adjustment. KRG is about 13”.Curious why you say chassis dont work until 12.5" lop?
XLR is close to 12.5 maybe a smidge longer.
ARs are only thing that I’ve found shorter but I think kiddos do better learning on bolts (I tried a SBR Grendel and I prefer a bolt).
Caveat: if you ditched an XLR folder and used the folder tube, you may get close to 12”.
Edit: I see your comment on chassis with a buffer tube…I haven’t tried that but if it’s adjustable that could make it shorter.


